Recuperative burners are used in fuel-fired industrial furnaces, heat treatment furnaces and similar installations of that kind. In use of these types of burner, fuel and combustion air are delivered separately to a point (usually a nozzle at the outlet end of the burner fuel pipe) where the fuel and air mix and are then ignited for combustion within the installation or possibly within a combustion chamber forming part of the burner. The burners are so designed that waste combustion products (waste gas) leaving the installation are caused to leave the installation by way of a passage within the burner so that incoming combustion air flowing to the burner nozzle by way of another passage can be preheated by heat exchange with the outgoing waste gas before the air is mixed with the fuel so as to "recoup" or recover from the waste gas at least a proportion of its waste heat to raise the overall efficiency of the combustion process.
British patent specification Nos. 1331427 and 1332125 describe recuperators typical of those which are currently on the market.